Known in the art is a particulate filter for trapping particulate matter which is contained in exhaust gas, wherein the particulate filter is provided with alternately arranged exhaust gas inflow passages and exhaust gas outflow passages and porous partition walls which separate these exhaust gas inflow passages and exhaust gas outflow passages from each other, micropore zones are defined at upstream sides of the partition walls, macropore zones are defined at downstream sides of the partition walls, a pore size of the partition walls in the micropore zones is set so that particulate matter and ash can be trapped by the partition walls at the micropore zones, a pore size of the partition walls in the macropore zones is set so that ash can pass through the partition walls at the macropore zones, and the partition walls at the micropore zones and the partition walls at the macropore zones are integrally formed (see PTL 1). In this particulate filter, the ash passes through the partition walls at the macropore zones, therefore the amount of the ash which is deposited on the particulate filter is kept down. As a result, the pressure loss of the particulate filter is kept from increasing due to the ash.
On the other hand, known in the art is an exhaust purification system for internal combustion engine which executes PM removal control which increases the temperature of the particulate filter to a PM removal temperature and maintains the same PM removal temperature while maintaining the particulate filter in an oxidizing atmosphere in order to remove the particulate matter which is trapped on the particulate filter.